Among the lingering mysteries of the Sean Bell shooting have been how many times the tall, stocky passenger in his car who sustained 19 gunshot wounds was actually shot, and how he lived to tell about it.

The day after Joseph Guzman, the passenger, took the witness stand in the trial of three detectives charged in Mr. Bell’s death, Joseph Guzman, the medical curiosity, became the center of attention on Wednesday as the surgeon who kept him alive on Nov. 25, 2006, testified. The surgeon, Dr. Albert Cooper, was in the trauma unit of Mary Immaculate Hospital that morning when the call came announcing that patients with multiple gunshot wounds were en route.

Dr. Cooper, fellow doctors and staff members convened in the trauma bay and waited, with little idea of what had just transpired, he said. Mr. Bell, Mr. Guzman and Trent Benefield had just left Mr. Bell’s bachelor party at the Club Kalua in Jamaica, Queens, when officers investigating the club followed them, believing the men were armed. In the confrontation that followed, five officers opened fire with 50 shots, killing Mr. Bell and wounding Mr. Benefield and Mr. Guzman.

Detectives Michael Oliver and Gescard F. Isnora face charges of first- and second-degree manslaughter, first-degree assault and misdemeanor charges of reckless endangerment. Detective Marc Cooper faces two charges of reckless endangerment. All three are on trial before Justice Arthur J. Cooperman, who is hearing the case in State Supreme Court in Queens without a jury.

Dr. Cooper was the prosecution’s last and, coincidentally, 50th witness in the so-called 50-shot case. He was called to establish the nature of the injuries, which are the basis for the assault charges. Prosecutors rested their case on Wednesday, and the defense is expected to call its first witness, Officer Michael Carey, who fired three shots and was not charged, on Thursday.

Mr. Guzman and Mr. Benefield were taken by ambulance to Mary Immaculate, and a quick look told Dr. Cooper what his priorities should be, he testified. Mr. Benefield had been shot in the calves and in one buttock and was crying out in pain, but Mr. Guzman was in a much more dire condition.

“He was telling me in somewhat of a mumbling voice that he should live and I should help him to live,” Dr. Cooper said. “He appeared to be confused and somewhat combative, which was indicative he was probably in severe pain.”

The doctors stabilized Mr. Guzman with an air tube and began a head-to-toe inspection of his body, finding 19 bullet holes, including several in his legs and his abdomen, at least one in his chest and one in his cheekbone, which appeared superficial, the result of a glancing shot.

“My clinical suspicion is he had some lung trauma,” Dr. Cooper said. “We immediately placed a chest tube, which yielded blood, a lot of blood.” Then, a more stressful sign: a catheter also yielded blood, suggesting internal injuries to his bladder or urinary system.

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The injuries of Joseph Guzman, who had 19 bullet wounds, were detailed on Wednesday during the trial of three detectives.

“His blood pressure’s stable, his airway’s stable, so I think I have a little time to do further investigation,” he said. CAT scans and X-rays showed bullets and bullet damage near a kidney and spillage from holes shot in his intestines.

“We made sure blood was available” and gave Mr. Guzman a tetanus shot, he said, and then Dr. Cooper began to operate with an incision to the patient’s belly and found blood there, he said. Doctors packed dressing in all four corners of the abdominal cavity, and then pulled it away, looking for blood and spillage from his digestive tract.

Dr. Cooper found both intestinal content and fecal matter from Mr. Guzman’s colon in the cavity. “It has very dangerous bacteria,” he said, which could lead to a deadly infection. The team quickly stapled the holes in the intestines and colon, removing one piece that was shredded, he said. They sealed up the cavity and sent Mr. Guzman to the intensive care unit, he said.

He said Mr. Guzman’s blood alcohol was 0.04, half the legal limit for driving. Mr. Guzman has said that he had just one vodka drink the entire night, leading a defense lawyer, James J. Culleton, to ask Dr. Cooper if the blood alcohol would be that high, especially in a man of Mr. Guzman’s size, with just one drink. The doctor said he did not know. Mr. Benefield’s blood alcohol was 0.11, he said.

Dr. Cooper said he took several pictures of Mr. Guzman’s bullet holes with his cellphone, for reference in creating the sketches that he admitted into evidence, but the pictures were not requested by prosecutors.

Dr. Cooper seemed to put to rest another lingering question about Mr. Guzman: exactly how many times he was shot.

The day of the shooting, Police Commissioner Raymond W. Kelly said Mr. Guzman had been shot “as many as 11 times.” Later, the police said he was shot “at least” 11 times. An assistant district attorney, Charles A. Testagrossa, said in opening statements on Feb. 25 that Mr. Guzman had 19 wounds, some of them exit wounds.

On the witness stand on Tuesday, Mr. Guzman said he was shot 16 times.

But Dr. Cooper had a different number.

The doctor, who continued to treat Mr. Guzman for months, found seven bullets inside him, he said. Subtracting seven from 19, that left 12 gunshot wounds, an even number.

“Bullets either go through you, or they stay in you,” he said. He deduced that the 12 wounds were caused by six bullets that passed through Mr. Guzman’s body, for a total of 13 bullets that struck him, three fewer than Mr. Guzman’s account, but more than enough to kill him.

“They were life-threatening injuries,” Dr. Cooper said, “if they are not treated in a timely fashion.”

A version of this article appears in print on , on page B2 of the New York edition with the headline: On Stand in Officers’ Trial, Surgeon Details Injuries to Passenger in Sean Bell’s Car. Order Reprints|Today's Paper|Subscribe